Weather Hold and Reschedule on an Exterior

Purpose

Make the call to coat or to hold on a stated set of numbers at a stated time, then handle the hold so it costs one day instead of a re-do. Weather failures do not show up on the day; they show up next spring as a peeling south wall or a north elevation that never fully hardened, and by then nobody can prove what the surface temperature was. The failures this prevents are a crew coating at first light onto a wall that is still condensing, an elevation started at 3 p.m. in October that never reaches cure before the overnight low, and a hold day where the masking is left up in the rain and the customer hears nothing until the following afternoon.

Scope

The go, hold and partial-hold decision on residential and small commercial exterior coating work: the gates read off the product, the morning readings, the decision time, the trajectory check through the day, what happens on site when the day is held, the re-prep on return, and the rebooking record.

It does not cover the wind gate for spraying, which the spray containment and overspray control standard owns, the substrate moisture gate and the drying-day rules, which the exterior wash and prep day standard owns, or the deck-specific temperature rules in the deck and fence staining standard. This SOP aggregates those gates into one daily decision rather than restating them.

Roles and responsibilities

Procedure

1. Write the product's own gates onto the job before the crew is dispatched. Read the label and data sheet for the coating and the primer, and copy the numbers onto the job sheet. Acceptance: a written gate sheet naming the minimum and maximum ambient and surface temperatures, the minimum temperature that must hold for the period after application the sheet states, the rain-free window, and any humidity limit, each with the product it came from. Wrong, and the stop rule: a job with no gate sheet does not get coated, because the alternative is a crew making the call from experience with a product they have used twice. Hazard: none, a desk step, and it is first because label directions are the binding authority in this trade and every number below is theirs, not this article's.

2. Take the morning readings and apply the dew point spread before anything is opened. Read ambient temperature and relative humidity on site, read or compute dew point on the same instrument, and take surface temperatures with an infrared thermometer on each elevation including the shaded one. Acceptance: surface temperature at or above the label's minimum on the elevation being coated, and surface temperature at least 5 F above the dew point, which is the long-standing industrial coatings practice from the SSPC and NACE joint surface preparation standards, in the edition your job specification calls out, binding on you only through that specification and superseded by the label where the label states something different. Wrong, and the stop rule: a spread under the gate means that elevation is held even when the air feels dry, because condensation forming under the film is invisible at application and shows as adhesion loss later. Hazard: none beyond footing, all readings taken from the ground or from a properly set ladder per the ladder standard.

3. Make the call at a stated time and let the office move before the customer's day starts. Set a go or no-go time of 07:00 and a customer notification deadline of 07:30, both shop defaults worth tuning to your market but not worth leaving unstated. Acceptance: readings phoned to the office by the decision time with the verdict, and the customer notified by the notification deadline with the reason and the next candidate date. Wrong, and the stop rule: if no decision has been made by the stated time, the day is a hold by default, because a crew that drives out and stands around burns the same hours as a hold and loses the redeploy. Hazard: none, a call, and it is a step because the most expensive weather decisions get made by drift rather than by anybody choosing.

4. Check the trajectory, not just the reading in your hand. Before starting an elevation, look at what the surface will do for the rest of the day and overnight: the shade line's movement, the forecast high, and the forecast overnight low against the temperature the label requires to hold after application. Acceptance: the forecast overnight low at or above the label's stated minimum for the period after application, and enough remaining daylight on that elevation for the film to set before the shade reaches it. Wrong, and the stop rule: an elevation that passes now and will fail in three hours is held now, not started and abandoned; a film that chills before it coalesces will not recover when the sun comes back. Hazard: afternoon starts push crews into low light and cold hands on ladders, so an elevation that cannot be finished inside the gate does not get started for the sake of the day's numbers.

5. Let the neighboring gates trigger the same hold, and log them the same way. Read the wind measurement the spray containment standard requires and the substrate moisture readings the exterior wash and prep day standard requires, and treat a failure of either as a hold on that elevation. Acceptance: the wind reading and the moisture readings logged on the same daily line as the temperature and dew point figures, with the elevation each belongs to. Wrong, and the stop rule: running a separate log for each gate means nobody sees that one elevation failed three different gates in a week, so all four numbers land on one line. Hazard: none at logging, and the underlying hazards belong to those standards, which govern their own operations in full.

6. Secure the site when the day is held, rather than walking away from it. Take down or fully secure masking, uncover plants that will cook or drown under cover, strike ladders and staging per the ladder standard, cover open material, and leave the site in a condition that survives the weather you just held for. Acceptance: no loose sheeting anywhere on site, no plant left under plastic past the day, ladders down, and every container closed and off the ground. Wrong, and the stop rule: masking left up through a rain event holds water against trim and against glazing seals, so any masking that cannot be secured comes off, and it is re-done rather than reused on return. Hazard: wet sheeting is a slip surface and a sail at once, so it comes off the wall at ground level rather than from a ladder, and nothing is left tied to a gutter or a downspout to take wind load overnight.

7. Re-prep on return rather than resuming from yesterday's numbers. After any rain, dew-heavy night or multi-day gap, take the morning readings again and re-take the substrate moisture readings the wash standard requires, replace any masking that took water, and re-check the surface for dust, chalk and pollen. Acceptance: a fresh full set of readings for the day, moisture at or below the wash standard's gate at every point it names with the worst point governing, and a wiped test area showing no transfer on a dark cloth. Wrong, and the stop rule: resuming on the strength of the readings from before the hold is the single most common way a weather hold still produces a coating failure, so no elevation is coated on a reading taken before the weather event. Hazard: the surface may be slick and the ground soft after rain, so ladder bases are re-checked and re-planked before anything goes up, per the ladder standard.

8. Rebook on the criteria, not just on a date. Give the customer the next candidate date and the numbers that have to be true on it, and log the hold with all of its readings against the job. Acceptance: a rebooking note naming the date and the gates, and a hold log entry carrying the day's temperature, dew point, moisture and wind readings. Wrong, and the stop rule: a rebooking that promises a date without the conditions sets up the same conversation twice, so the note says plainly that the date is a plan and the numbers are the rule. Hazard: none, correspondence from the office.

The record this produces

Per job, per day: ambient temperature, relative humidity, dew point, surface temperature by elevation, substrate moisture where taken, wind reading where spraying, the verdict, the time it was made and who made it, and the notification time. Per hold: what was secured, what masking was replaced on return, and the rebooked date. The estimator reads the hold log at the end of a season, because an address that holds four times every October is an address that should be sold as a summer job.

One run of this procedure, filled in

A four-elevation exterior repaint in mid October, waterborne acrylic body coat, crew of two. Step 1: gate sheet copied off the data sheet, minimum surface temperature 50 F, that same 50 F to hold for the 24 hours after application, and a 4 hour rain-free window from application. The hold period and the rain-free window are the label's, not this article's, and they are the two figures step 4 reads against.

Step 2 fails on one elevation. At 06:50 the meter read ambient 54 F and relative humidity 82 percent, with dew point 48 F. Surface temperatures read 50 F on the north elevation and 61 F on the south. North: 50 minus 48 leaves a 2 F spread, under the 5 F gate, so the north was held even though its surface temperature was exactly at the label's 50 F minimum, which is the case that catches crews. South: 61 minus 48 leaves 13 F, clear of the gate and above the minimum, so the south was a go.

Step 3: the call went in at 06:58 and the office notified the customer at 07:14 that the south and west would run and the north would not. Step 4 governed the afternoon. By 13:00 the north read 57 F surface with dew point at 47 F, which is 57 minus 47, or 10 F of spread, clearing both morning gates. It was still held, because the forecast overnight low was 43 F against the gate sheet's 50 F for the 24 hours after application, and there was no way to give the film that. South and west cleared the rain-free window too, with no rain forecast inside 4 hours of the last pass, so the crew finished those two instead.

Step 6 was not needed that day, because the site stayed in production. Two days later rain came through overnight and the following morning was a full hold, and the masking on the north elevation was taken off rather than left up. Step 7 on the return day: fresh readings taken, and the substrate moisture readings on the north elevation came back 12, 13 and 14 percent at the three points the wash standard names, all at or below its 15 percent gate with the worst point governing, so the north went on that morning with fresh masking. The lowest point within 2 ft of grade was the 14, which is the point that dries last and the reason the standard takes it.

References

• Coating product labels and technical data sheets, the binding authority on minimum and maximum application temperatures, the period the temperature must hold after application, humidity limits and the rain-free window.
• SSPC and NACE joint surface preparation standards, in the edition your job specification calls out and binding only where it does, the origin of the practice that surface temperature be at least 5 F above the dew point; the product label governs where it states otherwise.
• See related: the exterior wash and prep day standard for substrate moisture gates and drying days, and the spray containment and overspray control standard for the wind gate.
• See related: the ladder and scaffold setup standard for base condition after rain, and the exterior stucco and masonry recoat standard for its own film schedule and recoat windows.